X-ray imaging is a radiography method using straightness and attenuation of X-rays, and based on the amount of attenuation accumulated in the course of the X-rays passing through an imaging area, it provides an X-ray image of the internal structure of the imaging area. To achieve this, an X-ray imaging system includes: an X-ray generation apparatus configured to irradiate X-rays to a imaging area; an X-ray sensor disposed to face the X-ray generation apparatus with the imaging area therebetween, and configured to detect X-rays that have penetrated through the imaging area; and an image processing apparatus configured to construct a gray-level X-ray image of an internal structure of the imaging area by using X-ray projection data, as a detection result detected by the X-ray sensor.
In recent years, X-ray imaging has been rapidly evolving into DR (Digital Radiography) using digital sensors due to the development of semiconductor and information processing technologies, whereby image processing technology has also been developed and is used in various ways according to the purpose and application field. As an example, there is intra-oral X-ray imaging mainly used in dentistry. Intra-oral X-ray imaging is an X-ray imaging technology for obtaining an X-ray image of a limited imaging area of a subject, and is performed as follows: an X-ray sensor is placed inside the subject's mouth; and X-rays are irradiated from an X-ray generation apparatus outside the mouth to the X-ray sensor, thereby obtaining an X-ray image of a tooth and surrounding tissue that is disposed between the X-ray generation apparatus and the X-ray sensor. The intra-oral X-ray image has advantages of low distortion, excellent resolution and sharpness, and relatively low radiation exposure, so it is mainly used for implant treatment or endodontic treatment requiring high resolution.
A portable radiography device can utilize battery power to facilitate ease of use. Recently, the development of technology for rechargeable battery such as lithium-ion battery has led to the weight reduction of a high capacity battery. In order to charge the rechargeable battery, a charger is required. In many cases, a charging cradle serving also as a cradle of a portable device is provided along with the portable device. Although the charging cradle is placed in a close and prominent position such as on a device user's desk, the function of the charging cradle is limited to indication of the charging state by the LED color or on and off state of the LED, other than the above-mentioned cradle function. The residual battery capacity and the available time of the battery or the possible number of times of use cannot be exactly predicted before the device is completely discharged and becomes inoperative or fully charged, resulting in inconveniences such as interruption during use.